It is known that, in the current state-of-the-art, non-volatile semiconductor, memories are designed to work in operating voltage and power supply ranges which depend on the type of application for which the memory is intended to be used. For example, if the application requires low consumption, as in the case of cellular mobile telephones, it is necessary to use a low operating voltage for the non-volatile memory of the semiconductor, i.e., a voltage between 2.7 V and 3.6 V. For some applications, instead, the requirement is limited to the standard operating voltage, i.e., a voltage between 4.5 V and 5.5 V.
From the memory manufacturing point of view, the above differences in supply voltage required by the end consumer entail considerable management problems. Manufacturing devices which are identical except for the adopted supply voltage requires producing devices according to multiple methods which depend on the desired voltage. This of course entails the need to differentiate from the very initial steps of the manufacturing process, the production of devices that operate at standard voltage and of devices that operate at low voltage. This advance planning is required depending on which kind of device is being manufactured. Production is thereby not linked to actual market demand, since manufacturers are forced to plan their production in advance, without taking into account the requirements or trends of the market. The choice of the low-voltage or standard-voltage device is thus made before the so-called testing step during which the devices are tested.
In order to meet market demand, manufacturers are forced to form a considerable stock, so as to be ready to cope with any change in the trend of demand for devices operating with either voltage that the market may seek. The aim of the present invention is to provide an operating voltage selection circuit for a non-volatile semiconductor memory in which selection of the low operating voltage or standard operating voltage is made at the testing step of said devices rather than at the beginning of the manufacturing process of the memory.